package 一些算法竞赛测试题;

import java.util.ArrayList;
import java.util.List;
import java.util.Scanner;

/**
 * Created with IntelliJ IDEA.
 * Description:
 * User: a
 * Date: 2022-09-26
 * Time: 16:03
 */
public class Demo1 {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        int n = scanner.nextInt();
        int m = scanner.nextInt();
        int sum = 0;
        for(int i = n; i <= m; i++){
            if(i % 2 != 0){
                sum += i;
            }
        }
        System.out.println(sum);
    }
}
